1. Field of the Invention
The present invention relates to an apparatus for detecting the surface of a member to be ground, for detecting a projection attached to or formed on the surface of the member to be ground, a method of manufacturing feelers used in the surface detecting apparatus, and an automatic inspection/grinding apparatus for determining the presence or absence and position of a projection by inspecting the surface of a member to be ground and for grinding the detected projection by a grinding member.
2. Description of the Related Art
Liquid crystal displays (hereafter referred to as LCDs) are in widespread use as display units for displaying images converted into electric signals. An LCD has a polarizing film provided on, for example, an obverse-surface side of a liquid crystal, and light and darkness is formed on the polarizing film depending on whether or not the light transmitted through the liquid crystal is transmitted through the polarizing film.
A known LCD is arranged such that a color filter, in which very small color-component dyes of such as green, blue, and red are arranged in mosaic form, is interposed between the liquid crystal and the polarizing film, and the light transmitted through the polarizing film is adapted to produce the respective color components, so as to display a color image.
In the event that projections, foreign objects, or the like are attached to or formed on the surface of the color filter, and a gap is produced between the polarizing film and the color filter due to such projections, foreign objects, or the like, it becomes impossible to shield unnecessary light by the polarizing film, making it impossible to display a clear image. For this reason, it must be ensured that very small projections or foreign objects are not present on the surface of the color filter which is used for a color LCD.
In general, the allowable range of the projecting height of projections on the surface of the color filter used for the color LCDs is considered to be approximately 4 .mu.m or less, and projections or foreign objects which are greater than that range need to be removed from the surface of the color filter. In so doing, since the surface of the color filter is soft, it is necessary to pay utmost care not to apply an unnecessary external force to the surface, and the operation must be performed accurately and reliably.
As apparatuses for automatically grinding projections, foreign objects, or the like attached to the surface of such a color filter, apparatuses are known in which the surface of the color filter is measured by a laser length measuring machine or the like to detect a projection having a more-than-prescribed amount of projection and calculate its position, or the surface of the color filter is imaged by a CCD image sensor, the nonconforming projection is detected and its position is determined by calculating the image information thus obtained, and grinding is automatically performed by a grinding member on the basis of the result of calculation such that the projection is reduced to a predetermined size or less.
However, such an automated grinding apparatus is precision-constructed, has a complicated structure, and is therefore very expensive. For this reason, as a generally adopted method in the operation of grinding the surface of the color filter, the operator visually inspects the presence or absence of large projections or foreign objects on the surface of the color filter in a conventional manner. When large projections or foreign objects are found, the operator grinds them manually by small degrees by using a grinding member, such as a grinding tape with abrasive particles deposited thereon, so as to remove the projections or foreign objects.